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Project No.: 0317.00.005.580 Page 1 of 2

Project Name: Nanotechnology Treatment Review CBI?

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No

TELEPHONE CALL RECORD

Incoming

Outgoing

Date: 03/15/2013 Time: 1:00 am

pm

Company Name: VirginiaTech, CEINT ERG Staff Name: Kim Wagoner, Eva Knoth

Contact Name: Michael Hochella Contact Phone Number: 540-231-6227

General Subject: Request for Information on Nanomaterials Research

TOPICS DISCUSSED AND ACTION TAKEN

On March 15, 2013, we called Dr. Hochella to discuss information about nanomaterials and his current research 

within the Center for the Environmental Implications of NanoTechnology (CEINT). We first introduced Dr. 

Hochella to EPA’s effluent guidelines process and our current evaluation of nanomaterials in industrial 

wastewater. We then reviewed our study questions: Where should we focus our efforts, the primary 

manufacturers or the industries that use nanomaterials in development of secondary products? He began by 

noting that most nanomaterials are naturally occurring, except for carbon nanotubes (CNTs) and fullerenes. We 

should consider both the manufacturers of nanomaterials and industries that discharge nanomaterials in 

wastewater. Most industries may not be aware that nanomaterials are present in their waste streams. 

We asked him to discuss his research regarding nanomaterials in sewage sludge. He described how he and a 

PhD student, Bojeong Kim analyzed some sewage sludge samples that originated from the 2009 EPA Targeted 

National Sewage Sludge Survey (EPA 822-R-08-014). Originally, the survey analyzed sludge from 74 

municipal wastewater treatment plants (WWTPs) across the US for an extensive list of parameters from 

organics to heavy metals. The results were published and the samples were locked in storage. The identity of 

each sample was protected.

Dr. Hochella’s team wanted to reevaluate the samples for the presence of nanoparticles (which was not 

previously done). They began by looking at the samples with high silver concentrations under a SEM with back 

scatter imaging to screen for specific areas of the sample that many contain small particles with heavy elements. 

Then, they looked at those areas under a TEM to identify the composition of the small particles. They found 

silver nanoparticles as small as 3 nm, in the form of acanthite (silver sulfide). They also looked for other 

nanoparticles in the sludge, and found titanium dioxide (TiO2), zinc sulfide and iron sulfide nanoparticles. 

Additionally, they found that silver nanoparticles can easily sulfidize within minutes, at room temperature. 

Nanoparticle sulfidation is a reaction in which silver nanoparticles complex with sulfides (compounds with 

sulfur it an oxidation state of -2) to form Ag(2)S. They also found TiO2 and other transition metal nanomaterials 

at levels much higher than what would occur naturally, suggesting there is a manmade source of these materials 

discharged to POTWs. This finding suggests concern with the application of sewage sludge to agriculture fields

because of toxicity and exposure concerns.

We asked if, based on his research, nanomaterials are more likely to partition into the sludge or if they would 

end up in WWTP effluent. Dr. Hochella suggested that we contact Ralf Kägi of Eawag: Swiss Federal Institute 

of Aquatic Science and Technology who has conducted practical experiments using a pilot WWTP that may 

address this question. In general, a nanoparticle will not settle out of solution unless “attached to carbon bits” 

due to its size. He also indicated that TiO2 is very abundant in sludge and relatively unreactive, insoluble and 
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highly refractory. However, TiO2 is a concern with regard to possible impacts on soils because of its catalytic 

surface.

He then discussed the abundance of naturally occurring nanomaterials. “These far exceed manufactured 

nanomaterials by orders of magnitude.” Most metal oxides are naturally occurring. Fullerenes and CNTs are not 

found in nature, and Dr. Hochella recommended focusing on their presence and behavior. Biology may not be

evolved to handle these. 

We followed by asking if manufactured metal oxide nanoparticles would have a significant effect since these 

materials are already present in nature? Dr. Hochella responded that if the nanomaterials dramatically upset the 

concentration balance within an area, they could have a large effect (e.g., a new mining operation or sludge 

applied to land that has previously not been exposed to a concentrated metals source). He discussed the results 

of the CEINT mesocosm study, in which mesocosms were doped with manufactured silver nanoparticles to 

determine their fate in a natural wetland. As expected, the silver nanoparticles were sulfidized, but surprisingly 

had a biological effect on the microbial community and plant life at very low concentrations (one tenth of a

ppm). He also confirmed that there is no toxicity data for the impact of transformed nanoparticles in the 

environment.

We asked if manufactured nanomaterials are distinguishable from those that are naturally occurring. Dr. 

Hochella responded that TiO2 nanoparticles are probably not. Naturally occurring TiO2 nanoparticles have been 

found in rivers in Montana (pristine to industrial activity) that are identical to manufactured nanoparticles. He 

added that we cannot be completely sure if these are naturally occurring because nanoparticles (e.g. CNTs) have 

been shown to be transported long distances through the atmosphere.

We asked if he could summarize and connect the dots between current research and potential regulation. Dr. 

Hochella responded it is likely that we will not have to worry about most nanomaterials at the concentrations 

that are likely to be present in the environment because to date they haven’t seen any effects; however, he 

cautioned that we could be surprised. We need to continue doing research to be able to quickly investigate if or 

when something goes wrong in order to determine the cause of illness or effects of exposure. 

We asked if he could talk about promising analytical methods that could be used for detection or 

characterization of nanoparticles. He pointed us towards the National Nanotechnology Network (NNIN), a NSF 

grant program on its 10th year, which is currently proposing a Next Generation Network (NG-NNIN). It is a 

consortium of 14 universities that provides infrastructure, instruments and expertise to further research and help 

outside users solve problems related to nanotechnology. Virginia Tech heads up the geosciences node of the 

network. The NG-NNIN will expand to 18 universities.

Dr. Hochella requested that we update him on our progress and share any publicly-available reports resulting 

from our inquiry.